package com.zeus.common.utils.hash;

import java.io.Serializable;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

/**
 * Murmur3 32bit、64bit、128bit 哈希算法实现<br>
 * 此算法来自于：https://github.com/xlturing/Simhash4J/blob/master/src/main/java/bee/simhash/main/Murmur3.java
 *
 * <p>
 * 32-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#94 <br>
 * 128-bit Java port of https://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp#255
 * </p>
 *
 * @author looly,Simhash4J
 * @since 4.3.3
 */
public class MurmurHash implements Serializable {
    private static final long serialVersionUID = 1L;

    // Constants for 32 bit variant
    private static final int C1_32 = 0xcc9e2d51;
    private static final int C2_32 = 0x1b873593;
    private static final int R1_32 = 15;
    private static final int R2_32 = 13;
    private static final int M_32 = 5;
    private static final int N_32 = 0xe6546b64;

    // Constants for 128 bit variant
    private static final long C1 = 0x87c37b91114253d5L;
    private static final long C2 = 0x4cf5ad432745937fL;
    private static final int R1 = 31;
    private static final int R2 = 27;
    private static final int R3 = 33;
    private static final int M = 5;
    private static final int N1 = 0x52dce729;
    private static final int N2 = 0x38495ab5;

    private static final int DEFAULT_SEED = 0;
    private static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;

    /**
     * Murmur3 32-bit Hash值计算
     *
     * @param data 数据
     * @return Hash值
     */
    public static int hash32(CharSequence data) {
        return hash32(bytes(data, DEFAULT_CHARSET));
    }

    /**
     * Murmur3 32-bit Hash值计算
     *
     * @param data 数据
     * @return Hash值
     */
    public static int hash32(byte[] data) {
        return hash32(data, data.length, DEFAULT_SEED);
    }

    /**
     * Murmur3 32-bit Hash值计算
     *
     * @param data 数据
     * @param length 长度
     * @param seed 种子，默认0
     * @return Hash值
     */
    public static int hash32(byte[] data, int length, int seed) {
        int hash = seed;
        final int nblocks = length >> 2;

        // body
        for (int i = 0; i < nblocks; i++) {
            int i_4 = i << 2;
            int k = (data[i_4] & 0xff) //
                | ((data[i_4 + 1] & 0xff) << 8) //
                | ((data[i_4 + 2] & 0xff) << 16) //
                | ((data[i_4 + 3] & 0xff) << 24);

            // mix functions
            k *= C1_32;
            k = Integer.rotateLeft(k, R1_32);
            k *= C2_32;
            hash ^= k;
            hash = Integer.rotateLeft(hash, R2_32) * M_32 + N_32;
        }

        // tail
        int idx = nblocks << 2;
        int k1 = 0;
        switch (length - idx) {
            case 3:
                k1 ^= data[idx + 2] << 16;
            case 2:
                k1 ^= data[idx + 1] << 8;
            case 1:
                k1 ^= data[idx];

                // mix functions
                k1 *= C1_32;
                k1 = Integer.rotateLeft(k1, R1_32);
                k1 *= C2_32;
                hash ^= k1;
        }

        // finalization
        hash ^= length;
        hash ^= (hash >>> 16);
        hash *= 0x85ebca6b;
        hash ^= (hash >>> 13);
        hash *= 0xc2b2ae35;
        hash ^= (hash >>> 16);

        return hash;
    }

    /**
     * Murmur3 64-bit Hash值计算
     *
     * @param data 数据
     * @return Hash值
     */
    public static long hash64(CharSequence data) {
        return hash64(bytes(data, DEFAULT_CHARSET));
    }

    /**
     * Murmur3 64-bit 算法<br>
     * This is essentially MSB 8 bytes of Murmur3 128-bit variant.
     *
     *
     * @param data 数据
     * @return Hash值
     */
    public static long hash64(byte[] data) {
        return hash64(data, data.length, DEFAULT_SEED);
    }

    /**
     * Murmur3 64-bit 算法 <br>
     * This is essentially MSB 8 bytes of Murmur3 128-bit variant.
     *
     * @param data 数据
     * @param length 长度
     * @param seed 种子，默认0
     * @return Hash值
     */
    public static long hash64(byte[] data, int length, int seed) {
        long hash = seed;
        final int nblocks = length >> 3;

        // body
        for (int i = 0; i < nblocks; i++) {
            final int i8 = i << 3;
            long k = ((long)data[i8] & 0xff) //
                | (((long)data[i8 + 1] & 0xff) << 8) //
                | (((long)data[i8 + 2] & 0xff) << 16) //
                | (((long)data[i8 + 3] & 0xff) << 24) //
                | (((long)data[i8 + 4] & 0xff) << 32)//
                | (((long)data[i8 + 5] & 0xff) << 40) //
                | (((long)data[i8 + 6] & 0xff) << 48) //
                | (((long)data[i8 + 7] & 0xff) << 56);

            // mix functions
            k *= C1;
            k = Long.rotateLeft(k, R1);
            k *= C2;
            hash ^= k;
            hash = Long.rotateLeft(hash, R2) * M + N1;
        }

        // tail
        long k1 = 0;
        int tailStart = nblocks << 3;
        switch (length - tailStart) {
            case 7:
                k1 ^= ((long)data[tailStart + 6] & 0xff) << 48;
            case 6:
                k1 ^= ((long)data[tailStart + 5] & 0xff) << 40;
            case 5:
                k1 ^= ((long)data[tailStart + 4] & 0xff) << 32;
            case 4:
                k1 ^= ((long)data[tailStart + 3] & 0xff) << 24;
            case 3:
                k1 ^= ((long)data[tailStart + 2] & 0xff) << 16;
            case 2:
                k1 ^= ((long)data[tailStart + 1] & 0xff) << 8;
            case 1:
                k1 ^= ((long)data[tailStart] & 0xff);
                k1 *= C1;
                k1 = Long.rotateLeft(k1, R1);
                k1 *= C2;
                hash ^= k1;
        }

        // finalization
        hash ^= length;
        hash = fmix64(hash);

        return hash;
    }

    /**
     * Murmur3 128-bit Hash值计算
     *
     * @param data 数据
     * @return Hash值 (2 longs)
     */
    public static long[] hash128(CharSequence data) {
        return hash128(bytes(data, DEFAULT_CHARSET));
    }

    /**
     * Murmur3 128-bit 算法.
     *
     * @param data -数据
     * @return Hash值 (2 longs)
     */
    public static long[] hash128(byte[] data) {
        return hash128(data, data.length, DEFAULT_SEED);
    }

    /**
     * Murmur3 128-bit variant.
     *
     * @param data 数据
     * @param length 长度
     * @param seed 种子，默认0
     * @return Hash值(2 longs)
     */
    public static long[] hash128(byte[] data, int length, int seed) {
        long h1 = seed;
        long h2 = seed;
        final int nblocks = length >> 4;

        // body
        for (int i = 0; i < nblocks; i++) {
            final int i16 = i << 4;
            long k1 = ((long)data[i16] & 0xff) //
                | (((long)data[i16 + 1] & 0xff) << 8) //
                | (((long)data[i16 + 2] & 0xff) << 16) //
                | (((long)data[i16 + 3] & 0xff) << 24) //
                | (((long)data[i16 + 4] & 0xff) << 32) //
                | (((long)data[i16 + 5] & 0xff) << 40) //
                | (((long)data[i16 + 6] & 0xff) << 48) //
                | (((long)data[i16 + 7] & 0xff) << 56);

            long k2 = ((long)data[i16 + 8] & 0xff) //
                | (((long)data[i16 + 9] & 0xff) << 8) //
                | (((long)data[i16 + 10] & 0xff) << 16) //
                | (((long)data[i16 + 11] & 0xff) << 24) //
                | (((long)data[i16 + 12] & 0xff) << 32) //
                | (((long)data[i16 + 13] & 0xff) << 40) //
                | (((long)data[i16 + 14] & 0xff) << 48) //
                | (((long)data[i16 + 15] & 0xff) << 56);

            // mix functions for k1
            k1 *= C1;
            k1 = Long.rotateLeft(k1, R1);
            k1 *= C2;
            h1 ^= k1;
            h1 = Long.rotateLeft(h1, R2);
            h1 += h2;
            h1 = h1 * M + N1;

            // mix functions for k2
            k2 *= C2;
            k2 = Long.rotateLeft(k2, R3);
            k2 *= C1;
            h2 ^= k2;
            h2 = Long.rotateLeft(h2, R1);
            h2 += h1;
            h2 = h2 * M + N2;
        }

        // tail
        long k1 = 0;
        long k2 = 0;
        int tailStart = nblocks << 4;
        switch (length - tailStart) {
            case 15:
                k2 ^= (long)(data[tailStart + 14] & 0xff) << 48;
            case 14:
                k2 ^= (long)(data[tailStart + 13] & 0xff) << 40;
            case 13:
                k2 ^= (long)(data[tailStart + 12] & 0xff) << 32;
            case 12:
                k2 ^= (long)(data[tailStart + 11] & 0xff) << 24;
            case 11:
                k2 ^= (long)(data[tailStart + 10] & 0xff) << 16;
            case 10:
                k2 ^= (long)(data[tailStart + 9] & 0xff) << 8;
            case 9:
                k2 ^= data[tailStart + 8] & 0xff;
                k2 *= C2;
                k2 = Long.rotateLeft(k2, R3);
                k2 *= C1;
                h2 ^= k2;

            case 8:
                k1 ^= (long)(data[tailStart + 7] & 0xff) << 56;
            case 7:
                k1 ^= (long)(data[tailStart + 6] & 0xff) << 48;
            case 6:
                k1 ^= (long)(data[tailStart + 5] & 0xff) << 40;
            case 5:
                k1 ^= (long)(data[tailStart + 4] & 0xff) << 32;
            case 4:
                k1 ^= (long)(data[tailStart + 3] & 0xff) << 24;
            case 3:
                k1 ^= (long)(data[tailStart + 2] & 0xff) << 16;
            case 2:
                k1 ^= (long)(data[tailStart + 1] & 0xff) << 8;
            case 1:
                k1 ^= data[tailStart] & 0xff;
                k1 *= C1;
                k1 = Long.rotateLeft(k1, R1);
                k1 *= C2;
                h1 ^= k1;
        }

        // finalization
        h1 ^= length;
        h2 ^= length;

        h1 += h2;
        h2 += h1;

        h1 = fmix64(h1);
        h2 = fmix64(h2);

        h1 += h2;
        h2 += h1;

        return new long[] {h1, h2};
    }

    private static long fmix64(long h) {
        h ^= (h >>> 33);
        h *= 0xff51afd7ed558ccdL;
        h ^= (h >>> 33);
        h *= 0xc4ceb9fe1a85ec53L;
        h ^= (h >>> 33);
        return h;
    }

    /**
     * 编码字符串
     *
     * @param str     字符串
     * @param charset 字符集，如果此字段为空，则解码的结果取决于平台
     * @return 编码后的字节码
     */
    private static byte[] bytes(CharSequence str, Charset charset) {
        if (str == null) {
            return null;
        }

        if (null == charset) {
            return str.toString().getBytes();
        }
        return str.toString().getBytes(charset);
    }
}
